Separating Data and Logic Using Metaclasses

PyYYC Meetup - 26 July 2016

Franklin Koch

Version 0: The Basics

from pyyyc_v00 import *

this_pres = PyYYCPresentation(
    presenter='Franklin',
    topic='Metaclasses',
    time_limit=90.,
    nslides=10,
    slide_color=[0, 0, 0]
)

this_pres.summarize()

this_pres.time_per_slide()

this_pres.strains_eyes()

js_pres = PyYYCPresentation('JAVASCRIPT', 'RULES', 'PYTHON', 'DROOLS', 'LOLOL')

js_pres.summarize()

js_pres.time_per_slide()

js_pres.strains_eyes()

print(PyYYCPresentation.__doc__)

next_pres = PyYYCPresentation('Rowan and Franklin', 'Shoulder bags', '4:30', 10, 'white')

next_pres.summarize()

next_pres.time_per_slide()

next_pres.strains_eyes()

Version 1: A bit of validation logic

from pyyyc_v01 import *

this_pres = PyYYCPresentation(
    presenter='Franklin',
    topic='Metaclasses',
    time_limit=90.,
    nslides=10,
    slide_color=[0, 0, 0]
)

this_pres.set_nslides(15)

this_pres.nslides

this_pres.set_time_limit('whatever')

this_pres.time_limit = 'whatever'

this_pres.set_slide_color('red')

this_pres.slide_color

js_pres = PyYYCPresentation('JAVASCRIPT', 'RULES', 'PYTHON', 'DROOLS', 'LOLOL')

Version 2: Getting a bit more pythonic - Properties wrappers

from pyyyc_v02 import *

this_pres = PyYYCPresentation(
    presenter='Franklin',
    topic='Metaclasses',
    time_limit=90.,
    nslides=10,
    slide_color=[0, 0, 0]
)

this_pres.nslides = 15

this_pres.nslides

this_pres._nslides

this_pres.time_limit = 'whatever'

this_pres.slide_color = 'red'

this_pres.slide_color

Version 3: Separating logic with class inheritance

from pyyyc_v03 import *

this_pres = PyYYCPresentation(
    presenter='Franklin',
    topic='Metaclasses',
    time_limit=90.,
    nslides=10,
    slide_color=[0, 0, 0]
)

js_pres = YYCjsPresentation(
    presenter='Franklin',
    topic='How javascript rules and literally everything else drools. lolol',
    time_limit=5.,
    nslides=100,
    slide_color='green'
)

happy_pres = FreeSpiritPresentation(
    presenter='Moonflower',
    favorite_color=[255, 51, 153]
)

happy_pres.summarize()

Version 4: More subclassing...

from pyyyc_v04 import *

Version 5: Extracting more logic out of our classes

from pyyyc_v05 import *

confirmColor('red')

confirmColor([10000, .1, .3])

Version 6: Brief foray into wrappers

from pyyyc_v06 import *

Version 7: Can we remove more of the repetitive code...?

from pyyyc_v07 import *

this_pres = PyYYCPresentation(
    presenter='Franklin',
    topic='Metaclasses',
    time_limit=90.,
    nslides=10,
    slide_color=[0, 0, 0]
)

this_pres.slide_color = 'red'

this_pres.slide_color

this_pres._slide_color

Version 8: Git rid of old subclass structure

from pyyyc_v08 import *

Version 9: Refactor clunky __init__ function

from pyyyc_v09 import *

this_pres = PyYYCPresentation(
    presenter='Franklin',
    topic='Metaclasses',
    time_limit=90.,
    nslides=10,
    slide_color=[0, 0, 0]
)

new_pres = PyYYCPresentation()

new_pres.time_limit = '1:30'

new_pres.time_limit = 90.

new_pres.summarize()

new_pres.summarize = 'Oops, but that is just python...'

summarized_pres = PyYYCPresentation(
    summarize = 'Hmm, that is a bigger oops...'
)

nefarious_pres = PyYYCPresentation(
    presenter = 'Franklin',
    _presenter = 'Dr. Nefarious'
)

Version 10: Remove the __init__ logic away from your data entirely

from pyyyc_v10 import *

Version 11: Metaclasses. Finally.

from pyyyc_v11 import *

Version 12: Introspection with metaclasses

from pyyyc_v12 import *

pres = PyYYCPresentation()

pres.__class__.__name__

from pyyyc_v12 import *

pres = PyYYCPresentation()

pres._props

Version 13: Remove unnecessary redundancy (how's that for a section title?)

from pyyyc_v13 import *

this_pres = PyYYCPresentation(
    presenter='Franklin',
    topic='Metaclasses',
    time_limit=90.,
    nslides=10,
    slide_color=[0, 0, 0]
)

this_pres._slide_color

this_pres.slide_color = 'red'

this_pres.slide_color

this_pres._slide_color

Version 14: Validation on class definition (not instantiation)

from pyyyc_v14 import *

class SkateparkAccolades(WithSpecialProps):
    mad_props = StrProp()
    props = StrProp()
    def compliment(self):
        print('Dude, {props}. I mean seriously, {mad_props}!'.format(
            props=self.props,
            mad_props=self.mad_props
        ))

Version 15: Metaclass for auto-documentation

from pyyyc_v15 import *

PyYYCPresentation?

Version 16: Automatic class registration

import pyyyc_v16

pyyyc_v16._REGISTRY

for key in pyyyc_v16._REGISTRY:
    print(pyyyc_v16._REGISTRY[key].__doc__ + 60*'_' + '\n')

Version 17: Converting over to properties

from pyyyc_v17 import *

Version 18: Taking properties and running with it

from pyyyc_v18 import *

me = Person(name='Franklin', bio='python, 3ptscience, coffee')

slide1 = Slide(topic='PyYYC', slide_color='black')
slide2 = Slide(topic='Wrappers', slide_color=[100, 100, 100])
slide3 = Slide(topic='Metaclasses', slide_color='mediumslateblue')

ppt = PyYYCPresentation(
    presenter=me,
    topic='Data and Logic',
    time_limit=90.,
    slides=[slide1, slide2, slide3]
)

ppt.cliff_notes()

Learn More:

Visit our website, 3ptscience.com

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Use properties yourself!

pip install properties (or find it on Github, Docs, PyPI)

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Check out Steno3D, our online 3D visualization software: steno3d.com

pip install steno3d (or find it on Github, Docs, PyPI)

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Some good videos: Metaprogramming, Declarative interfaces, or just google python descriptors, wrappers, metaclasses...